Weakness is a reduction in the strength of one or more muscles.

Lack of strength; Muscle weakness

Weakness may be generalized (total body weakness) or localized to only one area, side of the body, limb, or muscle. Weakness is more notable when it is localized. Localized weakness may follow a stroke, flare up of multiple sclerosis, or injury to a nerve.

Weakness may be subjective or objective.

• Subjective means you feel weak, but there is no measurable loss of strength. For example, you may feel weak if you have infectious diseases such as mononucleosis and the flu.
• Objective means there is a measurable loss of strength noted during a physical exam.

Measurable weakness may result from a variety of conditions including metabolic, neurologic, primary muscular diseases, and toxic disorders.

METABOLIC

• Addison's disease
• Hyperparathyroidism
• Low sodium or potassium
• Thyrotoxicosis

NEUROLOGIC

• Amyotrophic lateral sclerosis
• Bell's palsy
• Cerebral palsy
• Guillain-Barre syndrome
• Multiple sclerosis
• Pinched nerve (for example, caused by a slipped disk in the spine)
• Stroke

PRIMARY MUSCULAR DISEASES

• Becker muscular dystrophy
• Dermatomyositis
• Muscular dystrophy (Duchenne)
• Myotonic dystrophy

TOXIC

• Botulism
• Organophosphate poisoning (insecticides, nerve gas)
• Paralytic shellfish poisoning

OTHER

• Anemia
• Myasthenia gravis
• Poliomyelitis

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Weakness Treatment

Review Date: 08/08/2009
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)